backend: support CLIENT_DEPRECATE_EOF

go.mod

@@ -9,9 +9,10 @@ require (
 	github.com/go-mysql-org/go-mysql v1.6.0
 	github.com/goccy/go-yaml v1.9.5
 	github.com/pingcap/errors v0.11.5-0.20211224045212-9687c2b0f87c
-	github.com/pingcap/tidb v1.1.0-beta.0.20220804075006-e071841317c5
-	github.com/pingcap/tidb/parser v0.0.0-20220804082206-fff748348776
+	github.com/pingcap/tidb v1.1.0-beta.0.20220819110652-8b5b724d8a93
+	github.com/pingcap/tidb/parser v0.0.0-20220819110652-8b5b724d8a93
 	github.com/prometheus/client_golang v1.12.2
+	github.com/siddontang/go v0.0.0-20180604090527-bdc77568d726
 	github.com/spf13/cobra v1.5.0
 	github.com/stretchr/testify v1.8.0
 	go.etcd.io/etcd/api/v3 v3.5.2
@@ -23,7 +24,7 @@ require (
 )
 
 require (
-	github.com/BurntSushi/toml v1.1.0 // indirect
+	github.com/BurntSushi/toml v1.2.0 // indirect
 	github.com/benbjohnson/clock v1.3.0 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
@@ -67,7 +68,7 @@ require (
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
 	github.com/pelletier/go-toml/v2 v2.0.1 // indirect
 	github.com/pingcap/failpoint v0.0.0-20220423142525-ae43b7f4e5c3 // indirect
-	github.com/pingcap/kvproto v0.0.0-20220711062932-08b02befd813 // indirect
+	github.com/pingcap/kvproto v0.0.0-20220804022843-f006036b1277 // indirect
 	github.com/pingcap/log v1.1.0 // indirect
 	github.com/pingcap/tipb v0.0.0-20220718022156-3e2483c20a9e // indirect
 	github.com/pkg/errors v0.9.1 // indirect
@@ -78,13 +79,12 @@ require (
 	github.com/prometheus/procfs v0.7.3 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20200410134404-eec4a21b6bb0 // indirect
 	github.com/shirou/gopsutil/v3 v3.22.6 // indirect
-	github.com/siddontang/go v0.0.0-20180604090527-bdc77568d726 // indirect
 	github.com/siddontang/go-log v0.0.0-20180807004314-8d05993dda07 // indirect
-	github.com/sirupsen/logrus v1.8.1 // indirect
+	github.com/sirupsen/logrus v1.9.0 // indirect
 	github.com/soheilhy/cmux v0.1.5 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	github.com/stathat/consistent v1.0.0 // indirect
-	github.com/tikv/client-go/v2 v2.0.1-0.20220729034404-e10841f2d158 // indirect
+	github.com/tikv/client-go/v2 v2.0.1-0.20220818084834-0d0ae0dcfb1f // indirect
 	github.com/tikv/pd/client v0.0.0-20220725055910-7187a7ab72db // indirect
 	github.com/tmc/grpc-websocket-proxy v0.0.0-20201229170055-e5319fda7802 // indirect
 	github.com/twmb/murmur3 v1.1.3 // indirect

go.sum

@@ -41,8 +41,8 @@ github.com/Azure/azure-sdk-for-go/sdk/azidentity v0.12.0 h1:VBvHGLJbaY0+c66NZHdS
 github.com/Azure/azure-sdk-for-go/sdk/internal v0.8.1 h1:BUYIbDf/mMZ8945v3QkG3OuqGVyS4Iek0AOLwdRAYoc=
 github.com/Azure/azure-sdk-for-go/sdk/storage/azblob v0.2.0 h1:62Ew5xXg5UCGIXDOM7+y4IL5/6mQJq1nenhBCJAeGX8=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/BurntSushi/toml v1.1.0 h1:ksErzDEI1khOiGPgpwuI7x2ebx/uXQNw7xJpn9Eq1+I=
-github.com/BurntSushi/toml v1.1.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
+github.com/BurntSushi/toml v1.2.0 h1:Rt8g24XnyGTyglgET/PRUNlrUeu9F5L+7FilkXfZgs0=
+github.com/BurntSushi/toml v1.2.0/go.mod h1:CxXYINrC8qIiEnFrOxCa7Jy5BFHlXnUU2pbicEuybxQ=
 github.com/BurntSushi/xgb v0.0.0-20160522181843-27f122750802/go.mod h1:IVnqGOEym/WlBOVXweHU+Q+/VP0lqqI8lqeDx9IjBqo=
 github.com/HdrHistogram/hdrhistogram-go v1.1.2 h1:5IcZpTvzydCQeHzK4Ef/D5rrSqwxob0t8PQPMybUNFM=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
@@ -69,7 +69,7 @@ github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bgentry/speakeasy v0.1.0/go.mod h1:+zsyZBPWlz7T6j88CTgSN5bM796AkVf0kBD4zp0CCIs=
 github.com/bketelsen/crypt v0.0.3-0.20200106085610-5cbc8cc4026c/go.mod h1:MKsuJmJgSg28kpZDP6UIiPt0e0Oz0kqKNGyRaWEPv84=
-github.com/blacktear23/go-proxyprotocol v1.0.0 h1:WmMmtZanGEfIHnJN9N3A4Pl6mM69D+GxEph2eOaCf7g=
+github.com/blacktear23/go-proxyprotocol v1.0.2 h1:zR7PZeoU0wAkElcIXenFiy3R56WB6A+UEVi4c6RH8wo=
 github.com/census-instrumentation/opencensus-proto v0.2.1/go.mod h1:f6KPmirojxKA12rnyqOA5BBL4O983OfeGPqjHWSTneU=
 github.com/certifi/gocertifi v0.0.0-20191021191039-0944d244cd40/go.mod h1:sGbDF6GwGcLpkNXPUTkMRoywsNa/ol15pxFe6ERfguA=
 github.com/certifi/gocertifi v0.0.0-20200922220541-2c3bb06c6054/go.mod h1:sGbDF6GwGcLpkNXPUTkMRoywsNa/ol15pxFe6ERfguA=
@@ -405,19 +405,19 @@ github.com/pingcap/failpoint v0.0.0-20220423142525-ae43b7f4e5c3/go.mod h1:4qGtCB
 github.com/pingcap/fn v0.0.0-20200306044125-d5540d389059 h1:Pe2LbxRmbTfAoKJ65bZLmhahmvHm7n9DUxGRQT00208=
 github.com/pingcap/goleveldb v0.0.0-20191226122134-f82aafb29989 h1:surzm05a8C9dN8dIUmo4Be2+pMRb6f55i+UIYrluu2E=
 github.com/pingcap/kvproto v0.0.0-20220510035547-0e2f26c0a46a/go.mod h1:OYtxs0786qojVTmkVeufx93xe+jUgm56GUYRIKnmaGI=
-github.com/pingcap/kvproto v0.0.0-20220711062932-08b02befd813 h1:PAXtUVMJnyQQS8t9GzihIFmh6FBXu0JziWbIVknLniA=
-github.com/pingcap/kvproto v0.0.0-20220711062932-08b02befd813/go.mod h1:OYtxs0786qojVTmkVeufx93xe+jUgm56GUYRIKnmaGI=
+github.com/pingcap/kvproto v0.0.0-20220804022843-f006036b1277 h1:4UQdx1acoUrQD0Q5Etz1ABd31duzSgp3XwEnb/cvV9I=
+github.com/pingcap/kvproto v0.0.0-20220804022843-f006036b1277/go.mod h1:OYtxs0786qojVTmkVeufx93xe+jUgm56GUYRIKnmaGI=
 github.com/pingcap/log v0.0.0-20200511115504-543df19646ad/go.mod h1:4rbK1p9ILyIfb6hU7OG2CiWSqMXnp3JMbiaVJ6mvoY8=
 github.com/pingcap/log v0.0.0-20210317133921-96f4fcab92a4/go.mod h1:4rbK1p9ILyIfb6hU7OG2CiWSqMXnp3JMbiaVJ6mvoY8=
 github.com/pingcap/log v0.0.0-20211215031037-e024ba4eb0ee/go.mod h1:DWQW5jICDR7UJh4HtxXSM20Churx4CQL0fwL/SoOSA4=
 github.com/pingcap/log v1.1.0 h1:ELiPxACz7vdo1qAvvaWJg1NrYFoY6gqAh/+Uo6aXdD8=
 github.com/pingcap/log v1.1.0/go.mod h1:DWQW5jICDR7UJh4HtxXSM20Churx4CQL0fwL/SoOSA4=
 github.com/pingcap/parser v0.0.0-20210415081931-48e7f467fd74/go.mod h1:xZC8I7bug4GJ5KtHhgAikjTfU4kBv1Sbo3Pf1MZ6lVw=
 github.com/pingcap/sysutil v0.0.0-20220114020952-ea68d2dbf5b4 h1:HYbcxtnkN3s5tqrZ/z3eJS4j3Db8wMphEm1q10lY/TM=
-github.com/pingcap/tidb v1.1.0-beta.0.20220804075006-e071841317c5 h1:ykpPpdxg7bJpsKUiMpvieknpPECqZVgChTUBENfQgTw=
-github.com/pingcap/tidb v1.1.0-beta.0.20220804075006-e071841317c5/go.mod h1:VaKuKfDKAu2fJA7U1WqGcrcNfOcTdIF9oX0IylG0FA4=
-github.com/pingcap/tidb/parser v0.0.0-20220804082206-fff748348776 h1:dvxE+3Vle5PH5TfDm+07VufqROyZatphja10bnA7I3c=
-github.com/pingcap/tidb/parser v0.0.0-20220804082206-fff748348776/go.mod h1:wjvp+T3/T9XYt0nKqGX3Kc1AKuyUcfno6LTc6b2A6ew=
+github.com/pingcap/tidb v1.1.0-beta.0.20220819110652-8b5b724d8a93 h1:t0wrJTmfqTPe8e7+AaUNiS0LJIegigflRWP6jnGxAco=
+github.com/pingcap/tidb v1.1.0-beta.0.20220819110652-8b5b724d8a93/go.mod h1:ibrqg2O6i98YbT6al8tpoz824bcHQlQKyV7VxpC1RH0=
+github.com/pingcap/tidb/parser v0.0.0-20220819110652-8b5b724d8a93 h1:nqdE7w2y4UNCfvudEZec6ijA6Ju+1AyvSISQgSvX8Ps=
+github.com/pingcap/tidb/parser v0.0.0-20220819110652-8b5b724d8a93/go.mod h1:wjvp+T3/T9XYt0nKqGX3Kc1AKuyUcfno6LTc6b2A6ew=
 github.com/pingcap/tipb v0.0.0-20220718022156-3e2483c20a9e h1:FBaTXU8C3xgt/drM58VHxojHo/QoG1oPsgWTGvaSpO4=
 github.com/pingcap/tipb v0.0.0-20220718022156-3e2483c20a9e/go.mod h1:A7mrd7WHBl1o63LE2bIBGEJMTNWXqhgmYiOvMLxozfs=
 github.com/pkg/browser v0.0.0-20180916011732-0a3d74bf9ce4 h1:49lOXmGaUpV9Fz3gd7TFZY106KVlPVa5jcYD1gaQf98=
@@ -478,7 +478,7 @@ github.com/shirou/gopsutil/v3 v3.22.6/go.mod h1:EdIubSnZhbAvBS1yJ7Xi+AShB/hxwLHO
 github.com/shopspring/decimal v0.0.0-20180709203117-cd690d0c9e24/go.mod h1:M+9NzErvs504Cn4c5DxATwIqPbtswREoFCre64PpcG4=
 github.com/shurcooL/httpfs v0.0.0-20190707220628-8d4bc4ba7749 h1:bUGsEnyNbVPw06Bs80sCeARAlK8lhwqGyi6UT8ymuGk=
 github.com/shurcooL/sanitized_anchor_name v1.0.0/go.mod h1:1NzhyTcUVG4SuEtjjoZeVRXNmyL/1OwPU0+IJeTBvfc=
-github.com/shurcooL/vfsgen v0.0.0-20200824052919-0d455de96546 h1:pXY9qYc/MP5zdvqWEUH6SjNiu7VhSjuVFTFiTcphaLU=
+github.com/shurcooL/vfsgen v0.0.0-20180711163814-62bca832be04 h1:y0cMJ0qjii33BnD6tMGcF/+gHYsoKQ6tbwQpy233OII=
 github.com/siddontang/go v0.0.0-20180604090527-bdc77568d726 h1:xT+JlYxNGqyT+XcU8iUrN18JYed2TvG9yN5ULG2jATM=
 github.com/siddontang/go v0.0.0-20180604090527-bdc77568d726/go.mod h1:3yhqj7WBBfRhbBlzyOC3gUxftwsU0u8gqevxwIHQpMw=
 github.com/siddontang/go-log v0.0.0-20180807004314-8d05993dda07 h1:oI+RNwuC9jF2g2lP0u0cVEEZrc/AYBCuFdvwrLWM/6Q=
@@ -487,8 +487,8 @@ github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPx
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
 github.com/sirupsen/logrus v1.6.0/go.mod h1:7uNnSEd1DgxDLC74fIahvMZmmYsHGZGEOFrfsX/uA88=
 github.com/sirupsen/logrus v1.7.0/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
-github.com/sirupsen/logrus v1.8.1 h1:dJKuHgqk1NNQlqoA6BTlM1Wf9DOH3NBjQyu0h9+AZZE=
-github.com/sirupsen/logrus v1.8.1/go.mod h1:yWOB1SBYBC5VeMP7gHvWumXLIWorT60ONWic61uBYv0=
+github.com/sirupsen/logrus v1.9.0 h1:trlNQbNUG3OdDrDil03MCb1H2o9nJ1x4/5LYw7byDE0=
+github.com/sirupsen/logrus v1.9.0/go.mod h1:naHLuLoDiP4jHNo9R0sCBMtWGeIprob74mVsIT4qYEQ=
 github.com/smartystreets/assertions v0.0.0-20180927180507-b2de0cb4f26d/go.mod h1:OnSkiWE9lh6wB0YB77sQom3nweQdgAjqCqsofrRNTgc=
 github.com/smartystreets/goconvey v1.6.4/go.mod h1:syvi0/a8iFYH4r/RixwvyeAJjdLS9QV7WQ/tjFTllLA=
 github.com/soheilhy/cmux v0.1.4/go.mod h1:IM3LyeVVIOuxMH7sFAkER9+bJ4dT7Ms6E4xg4kGIyLM=
@@ -522,8 +522,8 @@ github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PK
 github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/subosito/gotenv v1.2.0/go.mod h1:N0PQaV/YGNqwC0u51sEeR/aUtSLEXKX9iv69rRypqCw=
 github.com/tiancaiamao/appdash v0.0.0-20181126055449-889f96f722a2 h1:mbAskLJ0oJfDRtkanvQPiooDH8HvJ2FBh+iKT/OmiQQ=
-github.com/tikv/client-go/v2 v2.0.1-0.20220729034404-e10841f2d158 h1:oCtRW/f0FZabdoLuvqxIewcmHR83RlsdN37dS0EBRTU=
-github.com/tikv/client-go/v2 v2.0.1-0.20220729034404-e10841f2d158/go.mod h1:v3DEt8LS9olI6D6El17pYBWq7B28hw3NnDFTxQHDLpY=
+github.com/tikv/client-go/v2 v2.0.1-0.20220818084834-0d0ae0dcfb1f h1:/nr7P8uzJQ7u3wPEBHCokrsVmuDvi/1x/zI/ydk5n8U=
+github.com/tikv/client-go/v2 v2.0.1-0.20220818084834-0d0ae0dcfb1f/go.mod h1:v3DEt8LS9olI6D6El17pYBWq7B28hw3NnDFTxQHDLpY=
 github.com/tikv/pd/client v0.0.0-20220725055910-7187a7ab72db h1:r1eMh9Rny3hfWuBuxOnbsCRrR4FhthiNxLQ5rAUtaww=
 github.com/tikv/pd/client v0.0.0-20220725055910-7187a7ab72db/go.mod h1:ew8kS0yIcEaSetuuywkTLIUBR+sz3J5XvAYRae11qwc=
 github.com/tklauser/go-sysconf v0.3.10 h1:IJ1AZGZRWbY8T5Vfk04D9WOA5WSejdflXxP03OUqALw=
@@ -786,6 +786,7 @@ golang.org/x/sys v0.0.0-20210927094055-39ccf1dd6fa6/go.mod h1:oPkhp1MJrh7nUepCBc
 golang.org/x/sys v0.0.0-20220114195835-da31bd327af9/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220128215802-99c3d69c2c27/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220520151302-bc2c85ada10a/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.0.0-20220715151400-c0bba94af5f8/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20220728004956-3c1f35247d10 h1:WIoqL4EROvwiPdUtaip4VcDdpZ4kha7wBWZrbVKCIZg=
 golang.org/x/sys v0.0.0-20220728004956-3c1f35247d10/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=

pkg/proxy/backend/authenticator.go

@@ -30,7 +30,8 @@ const supportedServerCapabilities = mysql.ClientLongPassword | mysql.ClientFound
 	mysql.ClientConnectWithDB | mysql.ClientNoSchema | mysql.ClientODBC | mysql.ClientLocalFiles | mysql.ClientIgnoreSpace |
 	mysql.ClientProtocol41 | mysql.ClientInteractive | mysql.ClientSSL | mysql.ClientIgnoreSigpipe |
 	mysql.ClientTransactions | mysql.ClientReserved | mysql.ClientSecureConnection | mysql.ClientMultiStatements |
-	mysql.ClientMultiResults | mysql.ClientPluginAuth | mysql.ClientConnectAtts | mysql.ClientPluginAuthLenencClientData
+	mysql.ClientMultiResults | mysql.ClientPluginAuth | mysql.ClientConnectAtts | mysql.ClientPluginAuthLenencClientData |
+	mysql.ClientDeprecateEOF
 
 // Authenticator handshakes with the client and the backend.
 type Authenticator struct {
@@ -103,12 +104,9 @@ func (auth *Authenticator) handshakeFirstTime(clientIO, backendIO *pnet.PacketIO
 	if err = backendIO.WritePacket(clientPkt, true); err != nil {
 		return err
 	}
-	if err = auth.readHandshakeResponse(clientPkt); err != nil {
+	if err = auth.readHandshakeResponse(clientPkt, serverCapability); err != nil {
 		return err
 	}
-	if unsupported := serverCapability & auth.capability &^ supportedServerCapabilities; unsupported > 0 {
-		return errors.Errorf("server capability is not supported: %d", unsupported)
-	}
 
 	// verify password
 	for {
@@ -138,14 +136,17 @@ func forwardMsg(srcIO, destIO *pnet.PacketIO) (data []byte, err error) {
 	return
 }
 
-func (auth *Authenticator) readHandshakeResponse(data []byte) error {
+func (auth *Authenticator) readHandshakeResponse(data []byte, serverCapability uint32) error {
 	capability := uint32(binary.LittleEndian.Uint16(data[:2]))
 	if capability&mysql.ClientProtocol41 == 0 {
 		// TiDB doesn't support it now.
 		return errors.New("pre-4.1 MySQL client versions are not supported")
 	}
 	resp := pnet.ParseHandshakeResponse(data)
-	auth.capability = resp.Capability
+	auth.capability = resp.Capability & serverCapability
+	if unsupported := auth.capability &^ supportedServerCapabilities; unsupported > 0 {
+		return errors.Errorf("capability is not supported: %d", unsupported)
+	}
 	auth.user = resp.User
 	auth.dbname = resp.DB
 	auth.collation = resp.Collation
@@ -178,7 +179,7 @@ func (auth *Authenticator) readInitialHandshake(backendIO *pnet.PacketIO) (serve
 	if serverPkt, err = backendIO.ReadPacket(); err != nil {
 		return
 	}
-	if serverPkt[0] == mysql.ErrHeader {
+	if pnet.IsErrorPacket(serverPkt) {
 		err = pnet.ParseErrorPacket(serverPkt)
 		return
 	}

pkg/proxy/backend/backend_conn_mgr.go

@@ -17,6 +17,7 @@ package backend
 import (
 	"context"
 	"crypto/tls"
+	"encoding/binary"
 	"encoding/json"
 	"fmt"
 	"strings"
@@ -99,6 +100,7 @@ func (mgr *BackendConnManager) Connect(ctx context.Context, serverAddr string, c
 	if err := mgr.authenticator.handshakeFirstTime(clientIO, backendIO, serverTLSConfig, backendTLSConfig); err != nil {
 		return err
 	}
+	mgr.cmdProcessor.capability = mgr.authenticator.capability
 	childCtx, cancelFunc := context.WithCancel(ctx)
 	go mgr.processSignals(childCtx)
 	mgr.cancelFunc = cancelFunc
@@ -119,6 +121,18 @@ func (mgr *BackendConnManager) ExecuteCmd(ctx context.Context, request []byte, c
 		switch request[0] {
 		case mysql.ComQuit:
 			return nil
+		case mysql.ComSetOption:
+			val := binary.LittleEndian.Uint16(request[1:])
+			switch val {
+			case 0:
+				mgr.authenticator.capability |= mysql.ClientMultiStatements
+				mgr.cmdProcessor.capability |= mysql.ClientMultiStatements
+			case 1:
+				mgr.authenticator.capability &^= mysql.ClientMultiStatements
+				mgr.cmdProcessor.capability &^= mysql.ClientMultiStatements
+			default:
+				return errors.Errorf("unrecognized set_option value:%d", val)
+			}
 		case mysql.ComChangeUser:
 			username, db := pnet.ParseChangeUser(request)
 			mgr.authenticator.changeUser(username, db)

pkg/proxy/backend/backend_conn_mgr_test.go

@@ -423,3 +423,56 @@ func TestRedirectFail(t *testing.T) {
 	}
 	ts.runTests(runners)
 }
+
+// Test that the proxy sends the right handshake info after COM_CHANGE_USER and COM_SET_OPTION.
+func TestSpecialCmds(t *testing.T) {
+	ts := newBackendMgrTester(t)
+	runners := []runner{
+		// 1st handshake
+		{
+			client:  ts.mc.authenticate,
+			proxy:   ts.firstHandshake4Proxy,
+			backend: ts.handshake4Backend,
+		},
+		// change user
+		{
+			client: func(packetIO *pnet.PacketIO) error {
+				ts.mc.cmd = mysql.ComChangeUser
+				ts.mc.username = "another_user"
+				ts.mc.dbName = "another_db"
+				return ts.mc.request(packetIO)
+			},
+			proxy:   ts.forwardCmd4Proxy,
+			backend: ts.respondWithNoTxn4Backend,
+		},
+		// disable multi-stmts
+		{
+			client: func(packetIO *pnet.PacketIO) error {
+				ts.mc.cmd = mysql.ComSetOption
+				ts.mc.dataBytes = []byte{1, 0}
+				return ts.mc.request(packetIO)
+			},
+			proxy:   ts.forwardCmd4Proxy,
+			backend: ts.respondWithNoTxn4Backend,
+		},
+		// 2nd handshake
+		{
+			client: nil,
+			proxy: func(clientIO, backendIO *pnet.PacketIO) error {
+				backend1 := ts.mp.backendConn
+				ts.mp.Redirect(ts.tc.backendListener.Addr().String())
+				ts.mp.eventReceiver.(*mockEventReceiver).checkEvent(t, eventSucceed)
+				require.NotEqual(t, backend1, ts.mp.backendConn)
+				return nil
+			},
+			backend: func(packetIO *pnet.PacketIO) error {
+				require.NoError(t, ts.redirectSucceed4Backend(packetIO))
+				require.Equal(t, "another_user", ts.mb.username)
+				require.Equal(t, "another_db", ts.mb.db)
+				require.Equal(t, defaultClientCapability&^mysql.ClientMultiStatements, ts.mb.clientCapability)
+				return nil
+			},
+		},
+	}
+	ts.runTests(runners)
+}

pkg/proxy/backend/cmd_processor.go

@@ -31,6 +31,8 @@ const (
 
 // CmdProcessor maintains the transaction and prepared statement status and decides whether the session can be redirected.
 type CmdProcessor struct {
+	capability uint32
+	// Only includes in_trans or quit status.
 	serverStatus uint32
 	// Each prepared statement has an independent status.
 	preparedStmtStatus map[int]uint32